The excitement is over the affordability of the package. $10 is a nice price for a 2-cell PR bulb LED replacement. It only draws around 145mA. Do the math. That gives you DAYS of runtime on your cheapie 2 D-cell light. Should be more than 20 hours of runtime on a 2AA model light.
The light output is pretty good as well. I say it's a bit stronger than the River Rock 0.5W Luxeon, with a very bright hot spot and decent throw. The spill beam is TOTALLY dependant on the reflector design. I get great spill on the little $2 Garrity 2AA flashlight. The $8.99 2D Garrity has less spill and a brighter hot-spot.
The floating waterproof Eveready models are different as well. In the larger 2D model, the hot spot was very bright and very tiny and the spill was weak - I would not even consider using this bulb in that model. Yet in the smaller 2AA model, it was acceptable.
If you can disassemble your cheapie flashlight and put some diffusion on the lens, it really helps balance the hotspot-to-spill ratio on these bargain basement lights.
I didn't like it much on my 2D Maglite until I put some PDA screen protector on the inside of the lens as a diffuser. Smoothed it out nicely. It's not a Luxeon, but it's better than stock with "forever" run time.